1. Field of the Invention
The treatment of many cellular disorders, for example, tumors, involves the use of cytotoxic drugs. These drugs exert their activity in a variety of ways, usually interfering with a cellular function essential for the replication and/or viability of the cell. In many, if not most, instances, the drug is not specific for the unnatural cell, but rather tends to exert its effectiveness due to the more rapid proliferation of the abnormal cell, as compared to normal cells. While many organs of the body of a mammalian host regenerate cells rather slowly, there are also other organs, particularly bone marrow, which involves rapid proliferation of stem cells. Therefore, the cytotoxic agents not only can detrimentally affect the slowly regenerating cells, but also have a particularly pernicious effect on the immune system.
Despite the many disadvantages and side effects of employing the strongly cytotoxic drugs, they have found extensive application, because they have provided positive results. However, there is substantial interest in being able to employ the drugs in a manner which directs their activity toward the abnormal cells, in an effort to protect sensitive normal cells, both in the vicinity of and distant from the abnormal cell growth, from the harmful effects of the drug.
2. Description of the Prior Art
U.S. Pat. Nos. 4,322,398; 4,347,234; 4,349,530; and 4,391,797 describe implants and controlled release of drugs. Implantation of drugs in lesions is described in Maugh, Science (1981) 212:1128-1129; Macek et al., Abstracts of Immunology, 4109, p. 1053, Miyata et al., Cancer Research (1983) 43:4670-4675; McLaughlin et al., Cancer Research (1978) 38:1311-1316; and Bier et al., Cancer (1979) 44:1194-1200.